Abstract

HTI anisotropy induced by fractures. in unconventional reservoirs shows azimuthal variations. in amplitude and velocity. Identification of fractures. from seismic data requires wide azimuth data acquisition which have cost implications. Due to slump in oil pricing, new acquisitions may be difficult but the legacy 3D volumes may be re-processed with azimuthal workflows taking advantage of higher orders interpolation schemes and add value to exploration at a bare minimum cost. Here we have presented a case study to describe a pragmatic workflow to test and reprocess the vintage 3D with azimuthal consideration. In the present study one of the legacy 3D seismic shot with the orthogonal acquisition geometry, originally acquired for conventional reservoir objectives, have been used for azimuthal processing The aspect ratio of this dataset indicated its sub-optimal amenability to azimuthal processing. A feasibility study indicated that with 5D interpolation scheme, all required azimuth-offset classes could be populated reliably. The interpolated dataset was divided in six azimuth sectors and migrated; azimuthal moveouts were inverted using NMO equation as described by (Tsvankin 1997; Contreras et al. 1999). V, V and azimuth of Vind thus calculated were included in Azimuthal sectored Migration. Consequently "Snail gathers or COCA (common Offset Common Azimuth sorted) gathers exhibiting azimuthal moveout were corrected for HTI anisotropy.